Device for electric induction furnaces



Feb. 21, 1933. E. F. NORTHRUP DEViCE FOR ELECTRIC INDUCTION FURNACES Filed Aug. 22, 1931 Patented Feb. 21, 1933 UNITED: STATES PATENT OFFICE,

FITCH NOB'IHRUP, OF PRINCETON, NEW JERSEY, ASSIGNOR TO AJAX ELECTRO- 'I'HEBMIC CORPORATION, OF AJAX PARK, NEW JERSEY, A CORPORATION OF NEW JERSEY Application filed August 22, 1931. Serial No. 558,749.

ing trapped beneath the molten or heated char The purpose of the invention is to clear the water-cooled furnace inductor coil of water at the first sign of trouble so that in event of an arc formin between coil turns or between the charge an a turn, water cannot be forced into the charge through an opening made by such are.

Another purpose of the invention is to utilize an injector system to facilitate changing the feed water line, instantly, from pressure to suction.

Further purposes will appear in the speci fication and in the claims.

I have preferred to illustrate my invention by two figures. V

Fig. 1 is a combination line diagram and cross-section drawing showing as simply as possible the apparatus and assembly used in carrying out my methods.

Fig. 2 is a more detailed view of the injector, showing a slightly different arrange ment for the magnet and valve. Invisible or dotted lines are purposely left off for the sake 'of clearness.

In the drawing, similar numerals indicate like parts. g

In operating coreless induction furnaces of the type shown. in Fig. 1, it is possible for the wall refractory or container for the charge to wear away or to crack. When this occurs, the metal coming close to the inductor coil impairs the coil insulation and an arc may develop between coil turns or between a coil turn, the charge and another 0011 turn.

An are thus formed may cause the coil to ..be melted with the result that the cooling I have devised a means w ereb t water is forced through the opening and into the heated furnace. Water, converted to steam in this manner becomes trapped and may cause considerable damage due to exploslon. g

To prevent water bein forced 1n thusly, pressure on the water line is immediate y cut off or diverted.- In addition, I have arranged that the water be sucked back out of the coil to make even more remote the danger of an explosion.

I have shown in the figure one way by which an abnormal condition in the furnace may be made to operate the device. 'In this instance, as the arc occurs, a short circuit is imposed on the line and the line current rises. This current, operating through a relay, causes a magnet circuit to be open d. which trips the device.

I do not want to be limited to this method of control'b ut claim the use of the injector principle of changing pressure into suction in conjunction with coreless induction furnaces, however the emergency alarm may be glven.

Referring to the figures, I shall now describe in detail the operation of the device on which I claim protection.

In Fig. 1, the hollow'inductor coil 1. is connected to a source of alternating or pulsating current 2 by means of lines 3, 3 A condenser 4, is shunted across the coil to correct the power factor. The inductor coil surrounds the charge 5, in this case shown to be a bath of molten metal. The charge may be a solid mass without changing the princi le of my invention. A refractory contamer 6, holds the charge in place and insulates it from the inductor coil. Water is passed through the inductor coil from the inlet pipe 7 to the bottom turn on the furnace coil. This connectionto the furnace may be at bottom or top, or may be divided in an manner'without affecting the working 0 the device claimed. I have shown it connected to'the bottom because in this case the pressure of the water in the coil tends to flow back, thus aiding the suction in case of emergency. Likewise I have shown the injector assembly 8 placed near and low with respect to the inductor coil for the same reason.

The trap door 9 of the injector is nor mally closed. It is composed of a hinged gate of iron, lined with a piece of rubber or leather or similar material 10, to insure a water-tight joint. This gate or valve may be either solid or laminated and normally coil 12 wound around it.

is held closed against the emergency outlet pipe 11 by means of the magnet and solenoid 12. This magnet is energized by any control source 13 through lines 14:, 14 switch 20, and contactor 15. Contactor 14 and switch 20 are normally closed but contacts 15 will be opened in event of excess current flowing in the main power lines 3, 3 by means of the solenoid 1G, magnet 17. and transformer 18. The switch 20 and handle 21 offer additional electrical and mechanical means for operating the gate valve 9.

In normal operation, the lower gate to the injector is closed and'the water entering through pipe 7 is forced into the injector and back through pipe 19 to the furnace coil. 1

When a metal leak or other breakdown causes a short circuit 011 the coil, the current in lines 3, 3 increases and the transformer 18 causes more current to flow in the solenoid 16, and the magnet 17 is drawn away from the contacts 15. \Vhen contacts 15 open, the magnet coil holding gate valve 9 of the injector closed, is de-energized and the gate valve opens. lVhen the gate valve of the injector opens, pressure in pipe 19 is released and reversed, the injector water flowing down through pipe 11 causing a suction in pipe 19. This clears the line and furnace inductor coil of water.

The injector principle is well known, but for the sake of clearness, I have shown an enlarged view of an injector in Fig. 2. In this figure I have shown the pipe 11 to be of iron with the gate valve solenoid magnet The injectors in general are of brass or bronze, but I have shown the lower end changed to iron in the figure for the purpose set forth.

Having thus described my invention so that others skilled in the art may be enabled to practice the same, what I desire to secure by Letters Patent is defined in what is claimed.

1. In a coreless induction furnace system a hollow water cooled inductor coil, an in jector assemblyin the cooling system of said furnace and Valve means for closing the discharge end of the injector as sembly for forcing water through the inductor coil normally, or withdrawing water from said coil in event of trouble.

2. In an induction furnace system, a hollow artificially cooled inductor coil, an injector system through which a cooling medium is passed to the coil, and valve means in the discharge end of the injector system to convert the pressure of said cooling medium through the coil @asuction to withdraw said cooling medium from the coil.

3. In a coreless induction furnace system a hollow artificially cooled furnace inductor coil, an injector system with its injector arni connected in serieswith the furnace inductor Lessee? coil and valve means for opening and clos ing the dischargeend of said injector system to force the cooling medium through the inductor coil normally or to withdraw the cooling medium therefrom in event of trouble.

4. In a coreless induction furnace system a hollow artificially cooled furnace inductor coil, an injector system with its injector arm connected in series with the furnace inductor coil and electromagneticaily operated valve means for opening and closing the discharge end of said injector system to force the cooling medium through the inductor coilnor mally or to withdraw the cooling medium therefrom in event of trouble.

5: In a coreless induction furnace system a hollow artificially cooled furnace inductor coil, an injector system wits. its injector arm connected in series with the furnace inductor coil, a normally closed electromagnetically operated valve for opening and closing the discharge end of said injector system and a relay operatively connected between the power source for said furnace inductor coil and said discharge valve for opening said discharge valve in the event of trouble or damage to the coil.

EDWIN F. NORTI-IRUP.

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